The present invention relates to a method for measuring hemoglobin concentration in the blood in a circuit of a dialysis machine.
Generally, a dialysis machine of the known type comprises a first circuit for blood circulation, connected, when in use, to the circulatory system of a patient, a second circuit for the circulation of dialysate, and a filter, through which the first circuit passes the blood and the second circuit passes the dialysate. The filter comprises a semi-permeable membrane which, when in use, separates the dialysate from the blood, and permits an exchange of ions between the dialysate and the blood and the transfer of some of the blood plasma through the membrane. The first circuit comprises an arterial branch located up-line from the filter and a venous branch located down-line from the filter, while the machine comprises a peristaltic pump located in the arterial branch to convey the blood extracted from the patient to the filter. The first and second circuits are made from transparent flexible material, such as PVC, to ensure the asepsis of the circuit. The flexibility of the circuits facilitates their packaging and enables the flow to be blocked by a simple constriction of a section of the circuit, while the transparency makes it possible to visually inspect the liquids being conveyed in the circuit during use
There is a known way of determining the concentration of hemoglobin in the red corpuscles during the dialysis treatment, by means of highly accurate measurements of an intrusive kind, which require the laboratory examination of blood samples. Other dialysis machines enable non-intrusive measurements of the hemoglobin concentration to be made within the machine. The non-intrusive measurements made within the machine are markedly less accurate than laboratory measurements, but have the advantage of being provided in real time in such a way that the operating parameters of the dialysis machine can be corrected instantaneously.
The patent IT 1,240,489 discloses a method of measuring the hemoglobin concentration within the machine and in a non-intrusive way, by measuring the absorption of electromagnetic waves of the blood flowing in the arterial branch of the first circuit.
Hemoglobin is a protein contained in the red corpuscles, and its concentration modifies the pigmentation of the red corpuscles; the concentration of hemoglobin in the blood therefore depends on the quantity of red corpuscles contained in the blood and on the quantity of hemoglobin contained in the red corpuscles. To measure the absorption of electromagnetic waves by the blood, an emitter is used to emit a beam of electromagnetic waves having an emission intensity correlated with an emission signal, the beam of electromagnetic waves is made to strike a section of the circuit, and a beam of electromagnetic waves is detected by means of a receiver which emits a signal correlated with the reception intensity. The difference between the emitted intensity and the received intensity corresponds to the absorption, which is correlated with the hemoglobin concentration by a specific function.
Although the described method has been shown to provide an accurate measurement, laboratory tests conducted by the applicant have demonstrated that, in some cases of operation of the dialysis machine, the measurement made according to the method described above supplies values of hemoglobin concentration which deviate from the concentration values measured in the laboratory for the same type of blood.
The object of the present invention is to provide a method for measuring the hemoglobin concentration in the blood in a circuit of a dialysis machine in a non-intrusive way, and with a level of accuracy which is as close as possible to the level of accuracy of laboratory measurement.
According to the present invention, a method is provided for measuring the hemoglobin concentration in the blood in a circuit of a dialysis machine, the method comprising the measurement of the absorption of electromagnetic waves by the blood along one section of the said circuit, the values of the said absorption being correlated with the values of the said hemoglobin concentration; the method being characterized in that the values of at least one physical quantity of the blood, from the group comprising blood pressure, blood temperature and the rate of flow of blood along the said section, are measured, and the values of hemoglobin concentration in the blood are calculated as a function of the values of absorption and of the said physical quantity.
The present invention also relates to a circuit for the application of the aforesaid method.
According to the present invention, a blood circulation circuit for a dialysis machine is provided for the application of the method according to at least one of claims 1 to 12, characterized in that it comprises a connection forming the said section of the circuit, the said connection comprising a tube for subjecting the blood to the measurement of the absorption of electromagnetic waves and a chamber for subjecting the blood to the measurement of pressure.
The present invention relates to a device for measuring a characteristic of the blood in a circuit of a dialysis machine.
According to the present invention, a device is provided for measuring the hemoglobin concentration in a circuit of a dialysis machine comprising a connection forming a section of the said circuit, the said connection comprising a tube along which a measurement is made by means of beams of electromagnetic waves to determine the absorption of the blood, the hemoglobin concentration being correlated with the said absorption, the device being characterized in that it comprises at least one further sensor for measuring one of two quantities, namely the blood pressure and the blood temperature; the hemoglobin concentration being a function of the absorption and of the said quantity.